Thifluzamide is a compound that has high fungicide activity against rice sheath blight.
Because the time to use a chemical against rice leaf spot withering disease in the cultivation of rice plant is when the rice field is covered with a lesser amount of water, the rate of release and diffusion of effective ingredient affects the controlling effect significantly. However, since water solubility of thifluzamide is extremely low like 1.6 mg/l (20.degree. C.), it is desirable to develop a method that increases the rate of its release in water and improves its efficacy.